1. Field of the Invention
This invention relates generally to a system and method for detection of buried objects. More particularly, this system and method utilizes down-looking infrared (DLIR) sensors with or without ground penetrating radar (GPR) and metal detectors (MD) to locate landmines buried beneath ground level.
2. Discussion of the Related Art
Today landmines have become an enormous problem for both military forces and civilian populations. Unlike the landmines utilized during World War II and before, today's landmines may not necessarily be made of metal that can be easily detected by metal detectors. Very often these landmines may be made of plastic or other materials that are difficult to differentiate from the surrounding soil or other naturally occurring phenomena. Further, in the case of antitank mines, these mines may be buried relatively deep in the to ground, such as six inches or more. These antitank landmines are designed and positioned in the ground so that the weight of a person would not activate the mine. However, the weight of a vehicle would in most cases set off the mine. Of course, setting off such an antitank mine may also be caused by a tractor plowing a field long after the war is over.
Therefore, the military and other agencies have long desired a mechanism by which buried landmines may be detected and neutralized. One such mechanism is illustrated in FIG. 1 and was known as the Close-In Detection (CID) System, developed under the Mine Hunter/Killer (MH/K) advanced technology demonstration program for the United States military by TRW and subcontractors to TRW. The CID System comprises a vehicle 10 on which a sensor array 30 is attached to the front thereof. This sensor array 30 would be mounted to vehicle 10 by hydraulic lifts and would contain metal detectors (MD) as well as ground penetrating radar (GPR). In addition, a forward-looking infrared (FLIR) camera 20 would be mounted to the top of the vehicle 10 and aimed to cover a trapezoidal area 50 in front of the vehicle 10 and sensor array 30. The FLIR 20 as well as sensor array 30 would detect objects 40 positioned below the ground 60. The information from both the sensor array 30 and FLIR 20 may be combined to identify objects 40. The design and operation of the CID System is further detailed in a paper presented in April, 2001 at the SPIE AeroSense Conference 4394: Detection & Remediation Technologies for Mines and Minelike Targets VI, by S. Bishop et al. entitled “Improved Close-In Detection for the Mine Hunter/Killer System”, incorporated herein in its entirety by reference.
FIG. 2 is a top view of the CID System shown in FIG. 1 and also shows the FLIR field 50, vehicle 10 and sensor array 30. In addition, sensor array 30 is shown containing GPR 70 sensors and electromagnetic induction (EMI) coils 80 that act as metal detectors.
However, the CID System shown in FIGS. 1 and 2 has several drawbacks directly related to the FLIR 20. First, the FLIR 20 is a relatively expensive and complex piece of equipment due to the lens system and IR detectors contained therein. The FLIR 20 may cost as much as 50 percent or more of the cost of the vehicle 10 itself. Thus, repair and replacement of the FLIR 20 camera is also expensive. In addition, since the FLIR 20 camera views the FLIR field 50 in front of sensor array 30, the unification of the respective images to identify landmines located beneath ground 60 adds another layer of complexity to the system.
Still further, FIGS. 3A, 3B, and 3C are similar to the CID System shown in FIG. 1 with the exception that difficulties due to the usage of the FLIR 20 are more clearly illustrated. In FIG. 3A, a misalignment of FLIR 20 camera by as little as one degree will create a one foot placement error in the FLIR field 50 that would result in a one foot displacement of any buried objects 40 detected. Therefore, proper calibration of the FLIR 20 camera is absolutely essential for accurate identification of buried objects 40. Of course, in a military vehicle, such as vehicle 10, off road usage, or simply rough roads, will necessitate the frequent realignment of the FLIR 20 camera. This may be particular the case in an active combat area.
FIG. 3B further illustrates how a rough road having a bump as small as 2 and ¼ inches will cause a one-foot placement error in the FLIR field 50. Of course, a similar sized pothole would also generate a similar displacement error. Since bumps and potholes are frequent occurrences even in the best road systems, the accuracy of the FLIR 20 camera would be compromised.
FIG. 3C further indicates how a small rise in the road level may also generate a significant placement error. As indicated only a 4 and ½ rise can generate a one-foot placement error for objects 40 buried beneath ground 60.
FIG. 4 is an illustration of how reflected light from sky 65 may impact FLIR 20 camera. Depending upon the position of the sun and cloud patterns in sky 65, a reflection off of object 90 may be generated by sky 65. Depending on the weather conditions and whether the sun or moon is out, the object 90 may appear hotter or cooler to the FLIR 20 camera than would otherwise be detected relative to the ground 60. Therefore, the accuracy of the FLIR 20 camera is also comprised by weather conditions.
Therefore, what is needed is a device and method that will have the benefits of IR detection of landmines without the high cost of an FLIR camera. Further, these IR detectors should not require repeated or complex adjustments in order to operate properly and should not be affected by road or weather conditions.